poj3237--Tree 树链剖分

题意：三种操作 ①修改第i条边的权值为val，②把u到v路径上的所有边的权值 去相反数③求u 到v路径上最大的边权

线段树的区间更新还是不熟练，，一直搞不对调试了好久还是没对，最后还是看的kuangbin的代码。

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int inf = 0x3f3f3f3f;
const double eps = 1e-8;
const int maxn = 1e5+10;
struct
{
    int to,next;
}e[maxn<<1];
int head[maxn],edge;
void add(int x,int y)
{
    e[edge].to = y;
    e[edge].next = head[x];
    head[x] = edge++;
}
int son[maxn],fa[maxn],siz[maxn],dep[maxn];
void dfs(int root)
{
    siz[root] = 1;
    son[root] = 0;
    for (int i = head[root]; i > 0; i = e[i].next)
    {
        if (fa[root] != e[i].to)
        {
            dep[e[i].to] = dep[root] + 1;
            fa[e[i].to] = root;
            dfs(e[i].to);
            if (siz[e[i].to] > siz[son[root]])
                son[root] = e[i].to;
            siz[root] += siz[e[i].to];
        }
    }
}
int tot,top[maxn],li[maxn<<2],pos[maxn];
void build(int root,int father)
{
    top[root] = father;
    pos[root] = tot;
    li[tot++] = root;
    if (son[root] > 0)
        build(son[root],top[root]);
    for (int i = head[root]; i > 0; i = e[i].next)
        if (fa[root] != e[i].to && son[root] != e[i].to)
            build(e[i].to,e[i].to);
}

int minv[maxn<<2],maxv[maxn<<2], tt[maxn],lazy[maxn<<2];
void build_Segtree(int l,int r,int o)
{
    lazy[o] = 0;
    if (l == r)
    {
        minv[o] = tt[li[l]];
        maxv[o] =tt[li[l]];
        return;
    }
    int mid = (l + r) >> 1;
    build_Segtree(l,mid,o<<1);
    build_Segtree(mid+1,r,o<<1|1);
    minv[o] = min(minv[o<<1],minv[o<<1|1]);
    maxv[o] = max(maxv[o<<1],maxv[o<<1|1]);
}
char op[10];
int val;
inline void push_down(int l,int r,int o)
{
    if (lazy[o]&&l!=r)
    {
        maxv[o<<1] = -maxv[o<<1];
        minv[o<<1] = -minv[o<<1];
        maxv[o<<1|1] = -maxv[o<<1|1];
        minv[o<<1|1] = -minv[o<<1|1];
        swap(maxv[o<<1],minv[o<<1]);
        swap(maxv[o<<1|1],minv[o<<1|1]);
        lazy[o<<1] ^= 1;
        lazy[o<<1|1] ^= 1;
        lazy[o] = 0;
    }
}
void update(int l,int r,int o,int ua,int ub)
{
    if (ua <= l && ub >= r)
    {
        if (op[0] == 'N')
        {
            maxv[o] = -maxv[o];
            minv[o] = -minv[o];
            swap(maxv[o],minv[o]);
            lazy[o] ^= 1;
        }
        if (op[0] == 'C')
            minv[o] = maxv[o]  = val,lazy[o] = 0;
        return;
    }
    //if (op[0] == 'N')
    push_down(l,r,o);
    int mid = (l + r) >> 1;
    if (ua <= mid)
        update(l,mid,o<<1,ua,ub);
    if (ub > mid)
        update(mid+1,r,o<<1|1,ua,ub);
    minv[o] = min(minv[o<<1],minv[o<<1|1]);
    maxv[o] = max(maxv[o<<1],maxv[o<<1|1]);
}

int query(int l,int r,int o,int ua,int ub)
{
    if (ua <= l && ub >= r)
        return maxv[o];
    int mid = (l + r) >> 1;
    push_down(l,r,o);
    int t1 = -inf,t2 = -inf;
    if (ua <= mid)
        t1 = query(l,mid,o<<1,ua,ub);
    if (ub > mid)
        t2 = query(mid+1,r,o<<1|1,ua,ub);
    minv[o] = min(minv[o<<1],minv[o<<1|1]);
    maxv[o] = max(maxv[o<<1],maxv[o<<1|1]);
    return max(t1,t2);
}

int get_max(int ua,int ub)
{
    int f1 = top[ua];
    int f2 = top[ub];
    int tmp = -inf;
    while (f1 != f2)
    {
        if (dep[f1] < dep[f2])
            swap(ua,ub),swap(f1,f2);
        tmp = max(tmp,query(1,tot,1,pos[f1],pos[ua]));
        ua = fa[f1];
        f1 = top[ua];
    }
    if (ua == ub)
        return tmp;
    if (dep[ua]  > dep[ub])
        swap(ua,ub);
    return tmp = max(tmp,query(1,tot,1,pos[son[ua]],pos[ub]));
}
void get_negate(int ua,int ub)
{
    int f1 = top[ua];
    int f2 = top[ub];
    while (f1 != f2)
    {
        if (dep[f1] < dep[f2])
            swap(ua,ub),swap(f1,f2);
        update(1,tot,1,pos[f1],pos[ua]);
        ua = fa[f1];
        f1 = top[ua];
    }
    if (dep[ua] > dep[ub])
        swap(ua,ub);
    if (ua == ub)
        return;
    update(1,tot,1,pos[son[ua]],pos[ub]);
}

int d[maxn][3];
void init()
{
    int root,n;
    scanf ("%d",&n);
    root = (n + 1) >> 1;
    edge = tot = 1;
    memset(siz,0,sizeof(siz));
    memset(head,0,sizeof(head));
    fa[root] = dep[root] = 0;
    for (int i = 1; i < n; i++)
    {
        scanf ("%d%d%d",&d[i][0],&d[i][1],&d[i][2]);
        add(d[i][1],d[i][0]);
        add(d[i][0],d[i][1]);
    }
    dfs(root);
    build(root,root);
    build_Segtree(1,tot,1);
    op[0] = 'C';
    for (int i = 1; i < n; i++)
    {
        if (dep[d[i][0]] < dep[d[i][1]])
            swap(d[i][0],d[i][1]);
        tt[d[i][0]] = val = d[i][2];
        update(1,tot,1,pos[d[i][0]],pos[d[i][0]]);
    }
}
int main(void)
{
    freopen("in.txt","r",stdin);
    int t;
    scanf ("%d",&t);
    while (t--)
    {
        init();
        while (scanf ("%s",op),op[0] != 'D')
        {
            int x,y;
            scanf ("%d%d",&x,&y);
            if (op[0] == 'Q'&&x!=y)
                printf("%d
",get_max(x,y));
            if (op[0] == 'Q' && x == y)
                printf("0
");
            if (op[0] == 'C')
            {
                val = y;
                update(1,tot,1,pos[d[x][0]],pos[d[x][0]]);
            }
            if (op[0] == 'N'&&x!=y)
                get_negate(x,y);
        }
    }
    return 0;
}


/*
1
11
2 1 1
2 4 2
2 3 3
1 5 4
3 6 5
3 7 6
7 8 7
4 9 8
9 10 9
10 11 10
N 2 10
Query 4 10
DONE

*/